Abstract: In order to obtain the calculation method for the shear stiffness of headed stud connectors in composite bridges, 40 model specimens, divided into 14 groups, were prepared and tested. Based on the deformation and mechanical behavior of studs under shear forces, a formula for calculating the shear stiffness of stud connectors was proposed. The results show that the slip at the cut-off point of liner and nonlinear segments on a shear-slip curve is about 0.2mm. The secant modulus at the slip of 0.2mm is defined as the shear stiffness of stud connectors, and the corresponding shear force is about 45% of the ultimate shear force. The proposed formula indicates that the stud diameter, the elastic modulus of steel and concrete are the main influence factors of shear stiffness. And the shear stiffness predicted by the formula agrees well with test results.